Strange throttle angle....

[Damoegan]

Right, I've got a very strange problem that I need people to take a look at..

Myself and Dave (DPJ) fitted a INA mani last Sat and since then I've had a very strange boost problem.

Boost is dropping away at circa 4.5k rpm then picking back up 800-1k rpm later.. At the same time boost duty is dropping off too, as is airflow..

Here is the graphs from last weeks RR day

So today we set about set about logging to see if we can get to the bottom of whats going on. And we come accross a very strange throttle angle problem that has us baffled

First log

'003				'115			
Idle speed	Air mass in	Throt Angle	Ignit Angle	Engine Speed	Engine Load	Spec. Boost	Actual Boost
700-820 rpm	2.0-4.5 g/s	0.2-4.0%	0-12 BTDC	700-6800 RPM	15-150%	990-1800 mbar	<=1800 mbar
 /min	 g/s	%	 °BTDC	 /min	%	 mbar	 mbar
2560	69.97	100	12.8	2760	85.1	2100	1810
3040	119.33	99.2	13.5	3280	85.1	2070	2310
3560	134.75	100	9	3840	85.1	2040	2240
4160	160.14	100	9	4400	85.1	1970	2150
4600	169.61	99.6	19.5	4920	74.5	1940	2070
5160	167.86	37.6	16.5	5360	87.5	1990	2200
5560	170.92	36.5	13.5	5720	87.5	2010	2170
5960	181.19	38.4	15	6120	87.5	1940	2140
6240	182.58	36.9	18	6400	87.5	1850	2170
6520	182.64	36.5	16.5	6680	87.5	1810	2140
6800	179.47	36.9	18	6240	0	1000	1550
5280	173.17	92.5	13.5	5040	0	1000	2280

Note that the throttle angle cant hold 100%.......

Log #2

'003				'115			
Idle speed	Air mass in	Throt Angle	Ignit Angle	Engine Speed	Engine Load	Spec. Boost	Actual Boost
700-820 rpm	2.0-4.5 g/s	0.2-4.0%	0-12 BTDC	700-6800 RPM	15-150%	990-1800 mbar	<=1800 mbar
 /min	 g/s	%	 °BTDC	 /min	%	 mbar	 mbar
1920	42.47	100	15.8	1840	95.3	1740	1210
2160	58.75	100	12	2040	92.9	2030	1390
2480	78.81	100	10.5	2320	86.7	2050	1660
2840	108.08	100	7.5	2680	85.1	2090	1970
3320	123.39	100	12.8	3080	85.1	2070	2320
3760	137.39	100	16.5	3520	85.1	2010	2270
4240	158.36	100	9.8	4040	85.1	2010	2300
4720	171.89	100	18	4520	73.7	1950	2120
5120	182.86	99.6	18	4920	68.6	1910	2130
5520	185.31	99.2	18	5280	87.5	1950	2130
5840	187.56	100	20.3	5640	87.5	1980	2020
6120	188.69	100	21	6000	87.5	1980	1960
6400	194	100	14.3	6240	87.5	1910	1970
6600	195.06	100	13.5	6480	87.5	1840	1940

Throttle angle holds 100%

Log #3: At this point we hadn't noticed the throttle angle problem ad we were concentrating on boost. This log is with a MBC replacing the N75.

'003				'115			
Idle speed	Air mass in	Throt Angle	Ignit Angle	Engine Speed	Engine Load	Spec. Boost	Actual Boost
700-820 rpm	2.0-4.5 g/s	0.2-4.0%	0-12 BTDC	700-6800 RPM	15-150%	990-1800 mbar	<=1800 mbar
 /min	 g/s	%	 °BTDC	 /min	%	 mbar	 mbar
3480	137.11	99.6	8.3	3240	85.1	2110	2130
4120	155.33	100	17.3	3800	85.1	2050	2370
4480	146.78	32.5	18	4320	85.1	1990	2400
5000	137.11	32.2	12	4760	83.1	1970	2390
5400	171.08	34.1	12.8	5240	87.5	1980	2310
5840	172.14	36.5	20.3	5640	87.5	2010	2260
6120	177.86	36.9	18.8	6000	87.5	2010	2170
6440	182.92	36.9	13.5	6280	87.5	1910	2170
6680	181.92	37.3	18	6600	87.5	1840	2190
5640	15.28	8.6	11.3	6480	0	1000	1860

Log #4: Still with MBC.

'003				'115			
Idle speed	Air mass in	Throt Angle	Ignit Angle	Engine Speed	Engine Load	Spec. Boost	Actual Boost
700-820 rpm	2.0-4.5 g/s	0.2-4.0%	0-12 BTDC	700-6800 RPM	15-150%	990-1800 mbar	<=1800 mbar
 /min	 g/s	%	 °BTDC	 /min	%	 mbar	 mbar
1760	38.39	88.2	13.5	1920	95.3	1820	1210
2040	45.67	100	16.5	2160	89	2090	1420
2360	65.5	100	12	2480	85.1	2110	1720
2680	82.94	100	12	2840	85.1	2110	2030
3040	117.22	100	7.5	3320	85.1	2060	2440
3560	119.31	32.9	14.3	3720	85.1	2030	2490
3920	131.08	29.4	17.3	4160	85.1	2010	2480
4360	152.81	34.9	9.8	4520	71.8	1950	2260
4680	113	38.8	24	4840	74.9	1930	1950
5000	167.42	100	12	5200	87.5	1950	1970
5360	184.44	100	17.3	5560	87.5	2000	2030
5680	183.06	99.6	20.3	5880	87.5	1980	1960
6000	182.81	100	21	6160	87.5	1940	1950
6320	187.86	100	17.3	6400	87.5	1860	1920
6160	0	5.1	13.5	5480	0	1010	1140

Log #5: At this point we thought it could be a N75 fault so we Fitted Dave's N75 that we know is working fine.

'003				'115			
Idle speed	Air mass in	Throt Angle	Ignit Angle	Engine Speed	Engine Load	Spec. Boost	Actual Boost
700-820 rpm	2.0-4.5 g/s	0.2-4.0%	0-12 BTDC	700-6800 RPM	15-150%	990-1800 mbar	<=1800 mbar
 /min	 g/s	%	 °BTDC	 /min	%	 mbar	 mbar
2480	57.06	83.1	21.8	2360	0	1040	1150
2800	90.56	100	10.5	2600	85.1	1840	1470
3360	142.92	100	11.3	3080	85.1	2150	2140
3840	142.22	29.4	9	3600	85.1	2020	2540
4360	169.33	43.5	18.8	4080	85.1	2000	2540
4840	154.78	34.9	12	4600	72.5	1950	2410
5160	153.72	32.2	17.3	4960	70.6	1920	2190
5600	178.64	36.5	13.5	5480	87.5	1980	2350
5960	182.86	35.7	14.3	5800	87.5	1990	2260
6280	180.08	35.3	17.3	6160	87.5	1920	2210
6560	183.72	34.9	18.8	6440	87.5	1830	2260
6840	185.08	35.3	18	6720	87.5	1810	2260
6760	0	7.5	36	6960	81.2	1730	2210

Log #6: Still with Dave's N75

'003				'115			
Idle speed	Air mass in	Throt Angle	Ignit Angle	Engine Speed	Engine Load	Spec. Boost	Actual Boost
700-820 rpm	2.0-4.5 g/s	0.2-4.0%	0-12 BTDC	700-6800 RPM	15-150%	990-1800 mbar	<=1800 mbar
 /min	 g/s	%	 °BTDC	 /min	%	 mbar	 mbar
1960	41.53	98	17.3	2040	93.7	2030	1310
2160	58	100	15	2320	86.7	2060	1610
2480	78.92	100	9.8	2640	85.1	2080	1970
2840	108.94	99.6	6.8	3160	85.1	2060	2500
3400	117.97	28.2	15	3680	85.1	2000	2540
3920	143.92	29	9.8	4080	85.1	1990	2540
4360	163.69	36.1	9.8	4600	68.6	1940	2390
4720	129.75	30.6	19.5	4920	67.8	1890	2030
5040	149.61	34.9	19.5	5160	83.1	1920	2080
5320	179.08	36.1	18.8	5480	87.5	1970	2330
5680	175.64	35.7	18.8	5800	87.5	1980	2240
5960	182	36.5	21.8	6080	87.5	1940	2240
6200	184.25	36.1	18.8	6320	87.5	1880	2260
6440	186	35.3	15	6480	87.5	1820	2270

After all of this we removed and cleaned the TB but it had no effect at all.

Any thoughts whats going on

 

[DPJ]

It's like the ecu is pulling back on throttle angle! These are WOT runs, so the angle should show 100%..... (occasional 99.6)

No TB fault code - and it isn't random. It's repeatable. Done TBAs - (even videoed one with the tb off the car )

The other thing that is odd : load factor in 115 is showing the same figure as N75 duty cycle. )

 

[Damoegan]

Any more thoughts, Dave?

I'll upload the vid of the TBA for people to see soon.

 

[Damoegan]

TBA vid

 

[DPJ]

Yeah, I don't see how it can flow 185g/s + on a 35% throttle angle.

So, I think the throttle is open further, but a false reading is being reported. The ECU is acting on the false reading and pulling back. But what's it pulling back?

The airflow plainly drops, and imo that's the throttle plate closing a bit..... so on this, does the ecu keep trying to open it wider?

But if that's the case, why isn't there a throttle sensor fault code?

 

[Damoegan]

And both throttle position sensors seam to be doing what they should be doing when observed on vag-com...

 

[DPJ]

TBA vid

I should be working at Cape Canaveral with a countdown like that!

 

[Damoegan]

I should be working at Cape Canaveral with a countdown like that!

Lift off..

 

[DPJ]

And both throttle position sensors seam to be doing what they should be doing when observed on vag-com...

When you do a TBA in 060 - or press the throttle pedal with the engine off.

 

[CupraMVR]

hmmm seems very odd from them logs and what is happening you would think Vag-com would show up a fault with how its running. sorta of looks like a mapping issue with the way the boost drops off and comes back in.

maybe needs a AFR to check the fuelling aswell see what that is doing

 

[Damoegan]

Before fitting the INA mani everything was fine, John

Fueling seams fine, going off the AFR graph above and logging...

 

[DPJ]

hmmm seems very odd from them logs and what is happening you would think Vag-com would show up a fault with how its running. sorta of looks like a mapping issue with the way the boost drops off and comes back in.

maybe needs a AFR to check the fuelling aswell see what that is doing

Hi John! We decided not to bother with a fuelling log, because the fuelling from the RR run last Saturday seemed fine (see post #1) - Motorscope's sniffer is pretty acccurate.

I'd be interested to see 114 load - while you're logging you might as well do 031, Damien (with the N75 back in).

 

[Damoegan]

...I'd be interested to see 114 load - while you're logging you might as well do 031, Damien (with the N75 back in).

I'll try and get some tomorrow or Sat, Dave.

 

[DPJ]

Also to check....

ECU Block 062 – Accelerator Pedal
The DBW accerelator pedal has two position senders, G79 and G185, in a joint housing. The sender potentiometers are connected so that the voltage from G79 is twice the voltage from G185. The ECU converts the voltage values to percentage values, 5V corresponding to 100%.

Enter the ECU Measuring Block 062.
Press the accelator pedal slowly. The values in fields 3 and 4 should increase steadily. The tolerance ranges are 12% … 97% and 4% … 49%, respectively.
Check that the value in field 4 is about half of the value in field 3.
__________________

 

[Damoegan]

Hmmmm....


Back in a tick..

 

[Damoegan]

Field 3 shows ~80% and field 4 shows ~40%.......

 

[Damoegan]

 

[DPJ]

I've been through damaged wires / water etc in my head, but I can't see any of them giving such a predictable result.......

 

[Damoegan]

I've been through damaged wires / water etc in my head, but I can't see any of them giving such a predictable result.......

The thought had crossed my mind but, like you say, the results are to predictable...

 

[ibiza_95]

any chance you could swap the tthrottle body over from the other car you got the N75 off?

could be something inside that thats not loving it